This is an old revision of the document!
Table of Contents
Public NTP Servers
REMEMBER : Do NOT use burst or iburst against public NTP servers unless they are announced they accept it (e.g. don't use it against *.ntp.org servers). More details hre.
General NTP
There is a dedicated page to general NTP.
Infoblox NTP
There is a dedicated page to Infoblox NTP.
NTP Servers
It is best to use pool.ntp.org as an NTP server. This will find the closest available servers for you.
The 0, 1, 2 and 3.pool.ntp.org names point to a random set of servers that will change every hour. Also
- pool.ntp.org
- 0.pool.ntp.org
- 1.pool.ntp.org
- 2.pool.ntp.org
- 3.pool.ntp.org
More specific are:
- ntp0.ja.net (Stratum 1)
- ntp1.npl.co.uk (Stratum 2)
- time.cloudflare.com (Stratum 3)
- uk.pool.ntp.org
- 0.uk.pool.ntp.org
- 1.uk.pool.ntp.org
- 2.uk.pool.ntp.org
- 3.uk.pool.ntp.org
- europe.pool.ntp.org
- 0.europe.pool.ntp.org
- 1.europe.pool.ntp.org
- 2.europe.pool.ntp.org
- 3.europe.pool.ntp.org
NTP Servers
List of Stratum 1 servers
National Physics Laboratory hosts two public “Stratum 2” servers. This means their servers sync directly to atomic clocks.
DO NOT configure your system to use Google Public NTP together with non-leap-smearing NTP servers. e.g. do not combine Google NTP with Cloudflare NTP as they do not implement leap smearing. Smearing is used by Google, AWS, and Facebook NTP servers but not Cloudflare.
| Operator | Server FQDN | Server IP | Stratum | RefID | Source Type or FQDN | Delay | Location | Supports iBurst |
|---|---|---|---|---|---|---|---|---|
| Cloudflare | time.cloudflare.com | 162.159.200.1 | 3 | 10.21.8.19 | Internal Cloudflare? | 13.080 | UK | |
| Cloudflare | time.cloudflare.com | 162.159.200.123 | 3 | 10.21.8.19 | Internal Cloudflare? | 13.896 | UK | |
| Microsoft | time.windows.com | 51.145.123.29 | 3 | 25.66.230.5 | Internal Microsoft? | 13.896 | UK | |
| Zen Internet | ntp0.zen.co.uk | 212.23.8.6 | 2 | 195.66.241.3 | ntp1.linx.net | 11.642 | ||
| Zen Internet | ntp1.zen.co.uk | 212.23.10.129 | 2 | 85.199.214.99 | server1.quickdrivingtestcancellations.net | 16.948 | UK | |
| National Physics Laboratory | ntp1.npl.co.uk | 139.143.5.30 | 2 | 139.143.45.169 | ? | 16.457 | UK | |
| National Physics Laboratory | ntp2.npl.co.uk | 139.143.5.31 | 2 | 139.143.45.169 | ? | 17.329 | UK | |
| Manchester University | ntp2a.mcc.ac.uk | 130.88.202.49 | 2 | 193.62.22.66 | ntp0.ja.net | 22.581 | UK | |
| Manchester University | ntp2b.mcc.ac.uk | 130.88.203.13 | 2 | 130.88.203.13 | ntp0.ja.net | 22.282 | UK | |
| Manchester University | ntp2c.mcc.ac.uk | 130.88.200.6 | 2 | 193.62.22.66 | ntp0.ja.net | 22.135 | UK | |
| Manchester University | ntp2d.mcc.ac.uk | 130.88.212.143 | 2 | 193.62.22.74 | ntp1.ja.net | 22.771 | UK | |
| JANET, Harwell | ntp0.ja.net | 193.62.22.66 | 1 | .MSF. | MSF Radio Clock Receiver | 15.981 | UK | |
| JANET, Harwell | ntp1.ja.net | 193.62.22.74 | 1 | .MRS. | N/A | 26.042 | UK | |
| JANET, Harwell | ntp2.ja.net | 193.62.22.98 | 2 | 193.62.22.74 | ntp1.ja.net | 22.849 | UK | |
| JANET, Harwell | ntp3.ja.net | 193.62.22.90 | 1 | .PPS. | N/A | 26.305 | UK | |
| JANET, Harwell | ntp4.ja.net | 193.62.22.82 | 1 | .DCFa. | DCF77 | 17.528 | UK | |
| time.google.com | time1-time4 | 1 | Yes | |||||
| time1.google.com | 216.239.35.0 | 1 | .GOOG. | N/A | 20.393 | Yes | ||
| time2.google.com | 216.239.35.4 | 1 | .GOOG. | N/A | 20.399 | Yes | ||
| time3.google.com | 216.239.35.8 | 1 | .GOOG. | N/A | 20.514 | Yes | ||
| time4.google.com | 216.239.35.12 | 1 | .GOOG. | N/A | 22.899 | Yes | ||
| time.facebook.com | time1-time5 | 1 | Yes | |||||
| time1.facebook.com | 129.134.28.123 | 1 | .FB… | N/A | 25.595 | Yes | ||
| time2.facebook.com | 129.134.29.123 | 1 | .FB… | N/A | 16.803 | Yes | ||
| time3.facebook.com | 129.134.25.123 | 1 | .FB… | N/A | 12.037 | Yes | ||
| time4.facebook.com | 129.134.26.123 | 1 | .FB… | N/A | 18.341 | Yes | ||
| time5.facebook.com | 129.134.27.123 | 1 | .FB… | N/A | 16.546 | Yes | ||
| Apple | time.apple.com | 17.253.108.253 (and others) | 1 | .SHM. | 17.343 | Yes | ||
| Apple | time.euro.apple.com | 17.253.34.125 (and others) | 1 | .SHM. | 9.889 | Yes | ||
| Leo Bodnar Electronics | ntp1.leontp.com | 51.155.16.62 | 1 | .GPS. | N/A | 36.932 | UK | |
| Leo Bodnar Electronics | ntp5.leontp.com | 85.199.214.98 | 1 | .GPS. | N/A | 16.523 | UK | |
| Leo Bodnar Electronics | ntp6.leontp.com | 85.199.214.99 | 1 | .GPS. | N/A | 15.949 | UK | |
| Leo Bodnar Electronics | ntp7.leontp.com | 85.199.214.100 | 1 | .GPS. | N/A | 16.002 | UK | |
| Leo Bodnar Electronics | ntp8.leontp.com | 85.199.214.101 | 1 | .GPS. | N/A | 16.595 | UK | |
| Leo Bodnar Electronics | ntp9.leontp.com | 85.199.214.102 | 1 | .GPS. | N/A | 15.965 | UK | |
| Xentex IT Solutions | ntp.xtx.cloud | 81.133.66.177 | 1 | .PPS. | N/A | 24.301 | UK |
More information on Google's NTP offering can be found here. Google 'smear' a leap second over the course of a the hour either side of the leap second. Do not mix NTP servers that 'smear' and NTP servers that do not 'smear'.
Google uses its own NTP servers (see above) for its public DNS servers (see below). If you cannot configure multiple servers, time.google.com will automatically select an appropriate Google server nearby.